Low profile internal combustion engine

ABSTRACT

An internal combustion engine of the valve-in-head type having a low profile cylinder head which requires minimal head-room in the engine compartment of an automotive vehicle. The cylinder head has a rectilinear configuration with the valve trains disposed on horizontal axes extending transversely of the cylinder head. Each valve train in the cylinder head is provided with precise axial support at both ends of the train. The engine has a relatively thin upstanding combustion chamber over each cylinder and one or more pairs of poppet valves per cylinder each having a sealing surface adjacent its outer edge for engagement with respective seats defined by axially aligned header tubes. Each valve has a relatively short neck extending through the combustion chamber during the intake and compression strokes and when the fuel-air mixture is fired. The valve spring of each valve train is situated between a fixed abutment attached to the side wall of the cylinder head and the end of the valve cage remote from the poppet valves.

FIELD OF THE INVENTION

The invention relates generally to an internal combustion engine, andmore particularly to such an engine having improved fuel efficiency andemissions characteristics.

BACKGROUND OF THE INVENTION

Internal combustion engines derive power from a controlled combustion ofa mixture of a hydro-carbon based fuel and air inside a combustionchamber. A primary goal of any engine design is to increase fuelefficiency and performance while reducing emissions. A more completecombustion reduces emissions such as unburned hydro-carbons, (referredto herein "THC" emissions) as well as carbon dioxide (CO₂) and carbonmonoxide (CO). Of course, while complete combustion is desired, designtrade offs must be made since the processes leading to the most completecombustion may have negative side effects. For example, if the peaktemperature of combustion is too high, undue NO_(x) emissions will beformed during combustion and be exhausted. In addition, for a very hotflame front in the presence of cooler spots in the combustion chamber orcompression end of the cylinder, so-called "knock" may occur, thusreducing engine performance. Of course, a myriad of other considerationsgo into the design of any engine.

One means of increasing fuel efficiency while reducing emissions is toprovide a relatively fast burn of the combustion charge. The ideaunderlying such a design is that a faster burn will be more completesince the charge constituents (fuel and air) will preferably be close tothe point at which combustion is initiated when they are burned.So-called fast burn is typically achieved by virtue of engine designswhich seek to minimize the surface-to-volume ratio (S/V) of thecombustion chamber. The smaller S/V thus promotes a fast burn. By "fastburn" it is meant that the combustion is such that most of the pressureexerted on the piston by combustion is exerted over a small portion ofthe piston's travel which occurs just following ignition of the charge.Thus, while the high heat of the fast burn is advantageous in that itgives a more complete burning of the hydrocarbons, it may have thedisadvantage of leading to engine roughness and vibration by virtue ofsuch a large force being exerted during a small portion of the pistontravel. Moreover, such an engine must be designed such that the peaktemperature of combustion is high enough to get the desired hydrocarbonburning, but not so high as to generate undue NO_(x).

Another approach to achieving more complete combustion for fuelefficiency and emissions purposes is to increase the homogeneity of thecharge. A combustion charge may not be completely homogeneous, meaningthat certain regions are more volatile than others leading to unevencombustion. In one engine, to prevent such problems, the fuel-airmixture was subjected to an induced swirling motion prior to ignition toincrease the thoroughness of the mixture. As shown in U.S. Pat. No.4,846,138 this swirling was induced by the valve stems extending acrossa thin, upstanding combustion chamber during the compression stroke ofthe flat-headed piston. The valve stems serve to induce a swirl in thefuel-air mixture being compressed leading to a more thorough mixing.Further, during the power stroke, the same configuration of the valvestems causes the flame front to swirl around these stems again improvingthe combustion. As discussed in that patent, the swirling induced bythis configuration improved gas mileage and emissions for that engine.

The swirling during combustion in the engine according to the '138patent was also beneficial in removing unburned hydrocarbons from thewalls of the cylinder. Since the walls of the piston cylinder aretypically cooler than the internal volume of the cylinder, unburnedhydrocarbon molecules may cling to these walls during combustion. Theswirling induced by the valve stems in the '138 patent help to sweepthat charge around these cooler walls, thus assisting in removingunburned hydrocarbons. Such "scrubbing" of combustion chamber walls isthus a desirable feature for reducing such emissions.

While the extreme temperatures under which combustion typically occursare advantageous in terms of burning the fuel efficiently, it has otherdraw backs which must be compensated for in the engine design. Oneexample is in the valves associated with the combustion chamber. In atypical engine configuration, the intake and exhaust valves are disposedwithin the intake and exhaust ports which they are sealing. This isparticularly disadvantageous in the case of the exhaust valve since thatvalve sits in the stream of hot exhaust gas as it leaves the combustionchamber and exits through the exhaust port to the exhaust manifold.Alternatively, the intake valve is almost continually subject to vacuum.Further, because of the configuration of conventional valves and theirposition relative to the cam shaft, typical valves are very long andhave thin stems. Since flow to the stem away from the valve head is onemeans of heat transfer and dissipation, this means that a long thermaldistance must be traversed to effectively draw heat away from the headin this manner. Further, the stems are typically very thin, meaning thatonly a small radiating surface is available for radiating heat in thestem. The other mechanism for cooling standard valves is flow from thehead into the valve seat. Of course, this mechanism is unavailable whenthe valve is open and not in contact with the seat. Because typicalvalves are required to withstand incredibly high temperatures withouthaving adequate mechanisms for withstanding such temperatures, they aretypically formed of expensive and exotic materials so that they cansuccessfully withstand the elevated temperatures. It would thus bedesirable to avoid the undue expense and complexity of having to usesuch exotic materials for the valves.

A further consideration in regard to the valves is lubrication. A valveis generally actuated from a rotating cam shaft. In a typical singleoverhead cam, the cam contacts a cam pad at the end of a rocker arm.This contact causes the rocker arm to move the valve out of engagementwith its respective port. The cam pads on the rocker arm, however, aretypically located above the cam shaft, since the valves must be pulledout of engagement with their respective ports. As a result, lubricatingthis contact is problematic. Any oil that is thrown up to lubricate thecam/cam pad contact simply runs off due to gravity. A typical dualoverhead cam arrangement suffers from similar problems. There, a camengages the angled top surface of a bucket which houses the valvespring. Any oil thrown onto the top surface of the bucket also runs offdue to gravity. While the cams are sufficiently lubricated to allow theengine to function, such lubrication is less than ideal and worksagainst gravity, thus requiring an oversupply of oil to achievelubrication.

The lubrication mechanism for the valve train itself is also less thanideal although it works for its intended purpose. Since the valvesreciprocate in a bearing sleeve, there must be lubrication between thevalve and the sleeve. This lubrication is typically carried out by aplanned or intentional leakage of oil between the valve and the valvesleeve and past the valve seals. Thus, the valve seals are designed tohave less than ideal sealing characteristics. In the case of the intakevalve, the controlled leakage of oil in this manner is somewhat assistedby the fact that the intake port is constantly containing vacuum in theintake port. This assists in drawing lubricating oil between the bearingsleeve and the valve. Of course, this has the draw back of insuring thatat least a small amount of oil is burned during each combustion cycle ofa conventional engine. The exhaust valve, on the other hand, does nothave such a mechanism for assisting in the movement of oil between thevalve and the bearing sleeve. Because of the lack of such a mechanismthis means that the exhaust valve and intake valve in a given enginetypically see different amounts of oil, and are thus lubricateddifferently. Indeed, because of this, exhaust valves fail at asignificantly higher rate than intake valves. In addition, the only wayfor oil in the bearing sleeve of an exhaust valve to exit is to beexhausted through the exhaust port during the exhaust strike of thepiston with which a given valve is associated. This has negative impactin terms of emissions.

Lubrication of a typical valve train assembly is thus a difficulty whichmust be taken into account in engine design. Clearly, the system works,but extreme measures must be taken to compensate for the disadvantagesof such systems.

SUMMARY OF THE INVENTION

It is thus a primary aim of the invention to improve upon the structureof the internal combustion engine disclosed in U.S. Pat. No. 4,846,138to yield an engine that is more efficient than those providedheretofore, both in terms of combustion and valve performance.

In accord with that aim, it is a principal object of the presentinvention to provide a more complete combustion of the charge during thepower stroke.

It is a related object to both improve the mixing of the charge prior tocombustion, and to improve the removal of clinging fuel from the wallsof the combustion chamber and cylinder during combustion.

Another related object is to provide both vertical and horizontalcomponents to a swirling charge during combustion.

It is a further related object to provide a smooth and even burn of thecharge.

Still another object is reducing emissions generated during thecombustion process.

Another object of the invention is to provide for cooler valves than inexisting engines.

It is a related object to provide valves with short, efficient heatpaths.

It is a further related object to provide a circulating medium to carryheat away from the valves.

Another principal object of the invention is to provide a lubricationsystem for the valves and the valve-actuation mechanism that is assistedby the force of gravity.

A related object is to provide a system where the contact between thecam shaft and cam pad is adequately lubricated.

In accord with these and other objects of the invention, an internalcombustion engine is provided that uses the geometry of a combustionchamber, cylinder head, piston crown and valve necks extending acrossthe combustion chamber, to provide thorough mixing of the charge by aswirling action before combustion, and to provide a thorough and"smooth, even" burn of the charge after ignition by a complex verticaland horizontal swirling action that scrubs clinging fuel from the wallsof the combustion chamber and cylinder and provides a burn thatmaintains a higher pressure over a longer period of piston travel. Thepiston crown in the internal combustion engine is tapered to a zenithwhich is coincident with the longitudinal axis of the piston. Acomplementary interior surface is present in the cylinder head at thecompression end of the cylinder. Also provided is a thin upstandingcombustion chamber disposed vertically above the compression end of thecylinder and including a throat in communication with the interiorsurface of the cylinder head. The combustion chamber is divided into twosections which are offset with respect to the longitudinal axis. Thesectioning of the combustion chamber and the offsetting of thosesections aids in inducing the complex swirling of the charge during thecompression and power strokes of the piston. Associated with eachsection of the combustion chamber is a poppet valve which is disposedtransversely to the longitudinal axis such that the stem of each valveextends across each combustion section. Each poppet valve also includesa head and neck region, with the head selectively engaging a port in theopposite wall of the combustion chamber section. A resilient member iscoupled to each valve for biasing it into engagement with its respectiveport during the power and compression strokes to further induce swirlingof the charge.

This configuration gives the advantageous functional characteristicsreferred to above during the compression and power strokes. Duringcompression, the foregoing geometry results in the poppet valve necksserving as swirl sources to the compressing fuel-air mixture and thusinducing a substantially vertical swirling of that mixture. A similarswirling of the flame front occurs during combustion. At the same time,a complemental substantially horizontal swirling is induced andsustained by the two offset adjacent sections of the combustion chamberin combination with the tapered piston head and thecomplementally-shaped interior surface in the cylinder head. Theseparation of the chambers effectively divides the flame front into twosections during combustion. As the flame fronts emerge from thecombustion chamber, they contact the tapered region of the crown. Thiscauses the flame fronts to be thrown against the cylindrical walls ofthe cylinder, thereby aiding in providing a horizontal component to theswirl. As the piston withdraws, this complex swirling motion continues,thus scrubbing unburned hydrocarbons from the cylinder walls. Further,the initial restriction of the combustion to the two halves of thecombustion chamber, followed by entry of the flame fronts into thecylinder, provides a slower, more even burning of the charge than inprevious engines.

According to a further feature of the invention, hollow valves areadvantageously provided. These valves are larger in diameter than stockvalves and include an interior hollow region. Both the large exteriordiameter, and the hollow interior provide substantial radiative coolingsurfaces. Further, oil is circulated through and around the hollowvalves to provide for removal of heat through the medium of the oil.Further, the valves are not located in the ports which they seal as inconventional engines. This also leads to cooler valves since, forexample, the exhaust valve is exposed to the cool intake charge. Becauseof the enhanced cooling of these valves, exotic fabricating materialsare not required.

Further according to the invention, an internal combustion engine isprovided that uses the configuration and, optionally, the orientation,of the valve train to adequately lubricate the valve train and takeadvantage of the effects of gravity. In one embodiment, a rocker arm ismounted beneath the cam shaft for pivotal movement. One arm of therocker arm includes a cam pad for engaging a cam on the cam shaft.Another arm includes a valve-engaging end, such that a pivotal motion ofthe rocker arm causes movement of the valve. The rocker arm is partiallydisposed in a rocker arm bracket mounted below the cam shaft. Thebracket includes a central slot including sidewalls for receiving aportion of the rocker arm. The central slot and the enclosed portion ofthe rocker arm form an oil-receiving cavity for accumulating oil in thearea of the cam pad. This cavity includes crevices so that theaccumulated oil can leak out at a controlled rate by means of gravity.This leaking oil in turn flows into the respective valve associated withthe rocker arm. The valve train may be disposed at a downward angle withreference to the combustion chamber to which it is coupled, thusallowing the lubricating oil in the valve to flow away from thecombustion chamber, thus inhibiting the leakage of oil into the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partially cut-away view of the engine accordingto the invention;

FIG. 2 is a sectional view of the engine according to the invention;

FIG. 3 is a further sectional view, showing the engine according to theinvention during the compression stroke;

FIG. 4 is a similar view to FIG. 3, but showing the engine according tothe invention during the exhaust stroke;

FIG. 5 is an internal view of the combustion chamber according to oneembodiment of the invention, shown from below;

FIG. 6 is a section view of the combustion chamber according to anembodiment of the invention, which also shows the piston head;

FIGS. 7-9 depict progressions of the combustion process through variousstages;

FIG. 10 is a representation of the path taken by flame fronts as theyexit the combustion chamber;

FIG. 11 is a representation of the swirling action induced in the flamefront by the piston crown;

FIG. 12 is a further representation of continued swirling of the chargeduring combustion;

FIG. 13 is a representation of scrubbing of clinging fuel from the wallsof the combustion chamber according to the invention;

FIG. 14 is a representation of the relative orientation between thecombustion chamber and the piston crown;

FIG. 15 is a graph showing the comparative emission between an engineaccording to the invention and a stock engine;

FIG. 16 is a graph showing the percent of consumed charge (X) as afunction of the crank angle (θ) of the crank shaft for the inventive andstock engines;

FIG. 17 is a graph of the pressure volume curves comparing the inventiveand stock engines;

FIG. 18 is a top cut-away view of the head according to one embodimentof the invention;

FIG. 19 is an isolated view of the valve train according to anembodiment of the invention;

FIG. 20 is an exploded view of the valve train of FIG. 19;

FIG. 21 is a section view of a valve according to an embodiment of theinvention;

FIG. 22 is a representation of a piston crown according to analternative embodiment of the invention;

FIG. 23 is a section view of an alternative embodiment of the invention;

FIG. 24 is a further section of an alternative embodiment of theinvention, and showing a valve train in place;

FIG. 25 is a section view of a valve according to an alternativeembodiment of the invention;

FIG. 26 is an isolated view of the valve train according to thealternative embodiment;

FIG. 27 is an end view showing the push rod saddle according thealternative embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, FIG. 1 is a perspective view of anautomotive engine according to one embodiment of the invention. Theengine 10 includes a block 20, above which is disposed a cylinder head30. Cylinder head 30 is roughly trapezoidal in cross section, having awider base and narrower top. As the engine 10 is of a valve-in-headdesign, the cylinder head includes an intake port 40, and an exhaustport 50. According to a novel aspect of the invention, the cylinder headalso includes side-mounted valve enclosures 60 and 70, which house valveassemblies. It will be noted from FIG. 1 that the valve enclosures 60and 70 are mounted to the sidewall of the cylinder head at a dependingangle. This mounting angle, and the resulting angled position of theenclosed valves form an aspect of the present invention. The valvescontained within valve enclosures 60 and 70 are actuated by rocker armsdriven by a cam shaft. The rocker arms are shown in FIG. 1, and bearreference numbers 65 and 75. The cam shaft is shown at 80. As isapparent in FIG. 1, the rocker arms 65 and 75 are disposed within rockerarm brackets 66 and 76. FIG. 1 also shows a head cover 90 which may bebolted in place over the head by means of bolts 91.

The sectional view of FIG. 2 shows the various components of the engine10 in greater detail. In particular, FIG. 2 shows the valve structure100 according to an aspect of the invention. As discussed in regard tothe valve enclosure 70, valve 100 is preferably disposed at an upwardangle within the cylinder head 30 in this embodiment of the invention.Valve 100 is essentially a poppet valve with a head 105, a stem 107 andan angular sealing region 108 on the head 105. Sealing region 108 isdesigned to engage on a seat 58 in the exhaust port 50. Valve seat 58 isformed in a sidewall of an upstanding combustion chamber, depictedgenerally in FIG. 2 by reference numeral 120. As will be appreciated byone skilled in the art, both exhaust valve 100 and an associated intakevalve are associated with the combustion chamber 120. The valves aretimed by means of the cam shaft 80 so that both valves are closed duringthe compression and power strokes, and so that the exhaust valve is openduring the exhaust stroke, and that the intake valve is open during theintake stroke. Unlike a conventional engine, the neck of valve 100, andthe neck of the associated intake valve extend across the combustionchamber to close the exhaust and intake ports respectively. As such,with the valve 100 closed, the valve neck 107 extends across thecombustion chamber. As will be appreciated by those skilled in the art,valves are typically disposed within the ports which they seal.Accordingly, gases moving through those ports are impeded by the valvesand, particularly in the case of the exhaust ports, unduly heat thevalves. According to the present design, this does not occur. As seen inthe exhaust stroke represented in FIG. 4, the valve 100 in no wayimpedes flow through the exhaust port and conduit. Moreover, a typicalintake valve--in the intake conduit--is acted upon by vacuum almostconstantly. In this design, the valve is only subjected to vacuum duringthe intake stroke, thus reducing the chance of vacuum leaks.

It will also be noted from FIG. 2 that the combustion chamber itself hasa unique configuration. First of all, the combustion chamber 120 isrelatively thin and upstanding. Moreover, the combustion chamber 120according to the invention is divided into two halves or adjacentsections. The two adjacent sections are 121, shown in solid FIG. 2, and122, shown in phantom in FIG. 2. They are offset or canted with respectto each other about a vertical or longitudinal axis. A further view ofthe two sections 121 and 122 can be seen in the bottom section view ofFIG. 5. Just as the two adjacent sections of the combustion chamber areangled with respect to each other, so are each paired set of intake andexhaust valves associated with a given combustion chamber. As can beseen most clearly in FIG. 3, the exhaust valve 100 is tilted downwardlyin one direction while the intake valve 109 is tilted downwardly in theopposite direction. Since the sections of the combustion chamber withwhich each valve are associated are also tilted, this tilting of thevalves allows the longitudinal axis of the valve to be disposedperpendicularly to the port which is it designed to close.

Returning to FIG. 2, there is also shown, according to the invention, apiston 150. The piston 150 reciprocates within a cylinder within theblock 20. The crown of piston 150, bearing reference numeral 160, istapered. According to the invention, the crown 160 tapers toward azenith coincident with a vertical or longitudinal axis of the piston150. In the present embodiment, this tapering of crown 160 results in awedge shape, although other tapering shapes may be used. The wedge-shapeof the crown 160, according to this embodiment, can be seen by comparingFIG. 2, showing one side view and FIG. 6, showing the other side view.

Cylinder head 30 also includes an interior surface 130 which is adjacentto the compression end of the cylinder, and has a shape that iscomplemental to the wedge-shape of the piston crown 160. Thus, with thepiston 150 at the top of its stroke, the wedge-shaped crown 160 and thecomplemental interior surface 130 are disposed adjacent to each other,as seen in FIG. 2. Furthermore, the interior surface is in communicationwith the thin upstanding combustion chamber through a throat 135, thecontour of which can be seen most clearly in the section view of FIG. 5.

COMBUSTION

The configuration of the thin upstanding combustion chamber 120, thevalve stems which extend across it in the closed position, and theconfiguration of the piston crown 160 and the complemental surface inthe head, all combine to give the engine 10 improved performance andsignificant advantages in terms of emissions.

One advantage of this design is that the configuration of thesecomponents causes a controlled swirl of the charge during thecompression stroke. In reference to FIG. 3, the flow of the fuel-airmixture into the combustion chamber 120 is represented. As the piston190 nears the top of its stroke, the fuel-air mixture is forced or"squished" between the wedge-shaped piston crown 160 and thecomplementally shaped interior surface 130. The charge is then forcedupwardly through the throat region 135 between the combustion chamber120 and the interior surface 130. The compressed charge is thuschanneled into the combustion chamber. As the charge enters the twoadjacent sections 121, 122 of the combustion chamber it is forcedgenerally upwardly parallel to the axis of the respective adjacentsections. As the charge rises, it encounters the necks of the exhaustand intake valves, which are extended across the respective chamber intheir closed position as seen most clearly in FIG. 5. The valve necksthus serve as sources of intentionally induced swirling in thecombustion chamber during the compression stroke and thus inducedesirable turbulence in the combustion chamber. In particular, aswirling action of the compressed charge is induced in the charge as itattempts to circulate around the round valve stems, and as it comes incontact with the sidewalls of the combustion chamber, etc. This inducedswirl of the compressed charge insures a more homogeneous mixture offuel and air in the charge. The homogeneous nature of the charge helpsto ensure upon ignition, a more homogenous, smooth and even burning ofthe charge.

The configuration of the combustion chamber, valve stems, piston headand cylinder head surface also effect positive action in the combustionchamber during the combustion cycle of the power stroke. Once thecharge, which is under turbulence as discussed above, is fullycompressed (i.e. the piston is at the top of the compression stroke) thespark plug 160 ignites the charge. As can be seen from both FIGS. 3 and5, the spark plug, in this embodiment, is located along the horizontalline joining the tops of the two adjacent sections of the combustionchamber, and is also centrally located between the two chambers in atransverse direction. That is, the spark plug is centered at the top ofthe combustion chamber 120. As the charge ignites, the expanding flamefront interacts with the valve stems extending across the adjacentsections 121, 122 of the combustion chamber. A series of theoreticaldrawings showing the progression of the combustion process according tothe invention is shown in FIG. 7-13. The interaction of the flame frontF with the valve necks V (FIG. 7) forces the flame front to circulatearound the necks V, thus inducing a swirling in the advancing flamefront. Further, the flame front is effectively divided into threeseparate paths (labeled P1, P2 and P3 in FIG. 8). As the three flamefronts progress, they create a whirl path by pushing the unburned gasesin front of them. The center front, following path P2, is not ready tocollide and join with the fronts in paths P1 and P3 (see FIG. 9). At thesame time, the flame fronts in paths P1 and P3 are in contact with thecombustion chamber sections (C in FIG. 8) themselves, which are angledwith respect to each other as previously discussed (an isolated view ofthe combustion chamber and piston of the invention is shown in FIG. 14).The separation and angling of the adjacent sections of the combustionchamber serves to divide the emerging flame front into two sections,each one directed along an adjacent section of the combustion chamber.The two halves of the flame front, however, do not remain separated.Rather, because of the configuration of the combustion chamber and thepiston crown, they react and push on each other to induce a furthercomplex swirling of the expanding flame front that includes a horizontalcomponent.

It is believed that the interaction of the separated flame fronts toinduce this horizontal component to the swirl initially occurs adjacentthe throat area 135 between combustion chambers 120 and internal surface130 (see FIG. 3). During the time the expansion of the flame front andswirling are occurring in the combustion chamber (described above), theincreased pressure in front of the flame front is forcing the pistondownward. As the wedge-shaped crown 160 of the piston 150 and the pistonitself withdraw into the cylinder, the two halves of the flame front(one from each combustion chamber section) exit from the throat region135 into the compression end of the cylinder. The divided and swirlingflame front (indicated in FIG. 10 by references F1 and F2) thenencounters the wedge-shaped crown 160 of the piston as depicted in FIG.10. Indeed, the adjacent sections 121, 122 of the combustion chamber areangled so as to aim the separated flame fronts toward and respectivefaces of the crown 160 of the present embodiment (See FIG. 14). Becauseof the wedge-shape, the expanding flame front is again thrown outwardtoward the walls of the interior surface 130, and also toward the wallsof the cylinder. The flame fronts thus assume a rotational motion havinga significant horizontal as well as vertical component. This rotationalmotion is caused by the gases being thrown out to the cylindersidewalls, and by the interaction of the gases with the piston head asshown in FIG. 11.

The swirling motion continues, having both a vertical and horizontalcomponent, as the piston withdraws further into the cylinder. Because ofinertia and the directing of the flame fronts according to theinvention, each flame front which emerges from a combustion chambersection will follow a path like the exemplary one for flame front F1shown in FIG. 12. This significant swirling and directing of the flamefront during combustion not only assists in maintaining a slow, evenburn of the charge, but also leads to reduced emissions by virtue of a"scrubbing" action on the unburned hydrocarbons which typically stick tothe inner cylinder walls. The scrubbing action according to theinvention is shown in FIG. 13. The swirling flame front F is subject tocentrifugal loading, as indicated by the solid arrows. As the front F ispushed toward the cylinder wall W. it imparts sufficient energy to themolecules clinging to that surface to allow those molecules to liberatefrom the walls and be swept into the continuing combustion.

To summarize, a multiple flame front is initially created in thecombustion chamber by means of the valve necks dividing the initialflame front and inducing a largely vertical swirl therein. As the sametime, the angling of the two halves of the combustion chamber alsoserves to divide the flame front into two directed halves. These halvesexit the combustion chamber and engage the tapered crown of the pistonand are thrown out to the walls of the cylinder thereby creating ahorizontal component to the swirling, advancing flame front. Theoutward, rotational movement of the flame front also provides ascrubbing action to the cylindrical walls. A significant aspect of thiscombustion process is that the various swirling actions actually resultfrom the expansion of the flame front itself, as guided and directed bythe geometry of the combustion chamber according to the invention. In aconventional engine, the combustion initiates and accelerates the gases.In the present invention, the components are designed to also give thegas desirable direction and swirling to achieve enhanced performance andemissions levels.

It will be appreciated by one skilled in the art that the foregoingdescription of the combustion process represents an oversimplification.The variables affecting this process are too long to list. However, itis clear that the design of the combustion chamber, the valves, thepiston head and the cylinder head are such that the vertical andhorizontal components of the induced swirl referred to above will occurin the combusting charge. Indeed, close inspection of a prototype engineaccording to an embodiment of this invention exhibited swirl shaped burnmarks on the crown of the piston, confirming the existence of swirlingof the charge during combustion. Moreover, the existence of such amechanism for increasing the thoroughness of the combustion is evidentfrom the improved emission characteristics observed for an engineaccording to an embodiment of the present invention.

A graphical representation of those improved characteristics as comparedto the same characteristics for stock automotive engine is shown in FIG.15. As can be seen from that figure, the engine 10, according to theinvention, shows improved emissions characteristics for CO₂ ; CO; andNO_(x). The graph also shows a poorer emission result in terms ofunburned hydrocarbons (THC). It is believed that the superior CO and CO₂emissions are a result of the swirling actions induced in the combustionchamber and the compression end of the cylinder as discussed above. Themore thorough burning due to increased homogeneity of the charge and dueto the scrubbing action of unburned charge from the walls contributes tothis improvement. Although the actual emission levels for THC werehigher in the engine according to the invention, the level stillindicates an improvement over the stock engine. This is due to the factthat the present engine has a much larger surface-to-volume ratio (S/V)than a stock engine. Typically, a large S/V leads to a significantincrease in THC--due mainly to the large surface area being generallycooler and reducing the combustion temperature. In the present engine,the S/V is around 3-4 times larger than the stock engine, but the THCemissions are comparable. This is an indication that the uniquecombustion properties of this engine greatly enhance the level ofhydrocarbon burning during combustion--most probably due to the swirlingof the charge sustaining the burn, and due to the scrubbing action ofthe swirling charge. Moreover, the prototype engine according to thisembodiment exhibited superior mileage to the stock engine: 27.2 asopposed to 22:2 mpg. A modified stock engine was used to generate the"stock" data shown in FIG. 10. That engine was a Ford 2.3 liter SOHC4-cylinder engine. The engine had a 9.5:1 compression ratio. The enginewas operated with a Holley two barrel carburetor and Mallory aftermarket points ignition. Standard Ford intake and exhaust manifolds wereused, but the electronic ignition and fuel injection were deleted tomake the stock engine and the engine according to the inventionidentical except for the cylinder heads.

It is also believed that the configuration of the combustion-relatedcomponents leads to a smoother, even burn during combustion than inconventional engines. The smoothness of the burn, as compared to that ofa stock engine, can be seen in FIG. 16. That plot shows the percent ofconsumed charge (X) as a function of the crank angle (θ) of thecrankshaft and was generated with the two engines running at 3800 RPMand 99% load. As will be appreciated by one skilled in the art, theshape of such curves will differ for different RPM and load conditions.The central curve (S) is the fuel consumption curve for the stockengine. The left dashed curve I1 is the actual fuel consumption curve ofan engine according to the invention, and the second dashed curve I2 isthe same as I1, but displaced in time so that the spark ignition time ofI2 coincides with that of S. As this graph shows, the burn of the stockengine has a very steep slope, indicating that most of the combustionoccurs over a small range of crank angles. Curve I2, however, shows asmoother, less steep curve, showing that the combustion in the inventiveengine is more gradual and constant. It is believed that a primary causeof this smoother burn is the configuration of the combustion chamber andcylinder. While the combusting charge is in the combustion chamber, itis somewhat restricted by the small size of the chamber, and thepresence of the valve necks. Upon exiting into the compression end ofthe cylinder, the flame front is less restricted and is subject to theswirling and scrubbing action discussed previously. These differentphases of combustion apparently lead to the smoother burncharacteristics shown in FIG. 16. Such a burn may also be referred to asa "long" burn, since more constant pressure is exerted on the pistonover a longer portion of its travel, as compared to the burn of aconventional engine.

The smoother burn characteristics also mean that the pressure applied tothe piston face in the engine according to the invention is moreuniform. A pressure-volume curve comparing the stock engine and theinventive engine is shown is FIG. 17. This curve was generated with thetwo engines running at 3800 RPM and 99% load. As will be apparent to oneof skill in the art, the shape of these curves will differ for differentRPM and loading conditions. As can be seen, the curve for the inventiveengine I is broader than that of the stock engine S. This is firstly anindication of the more even burning of the engine according to theinvention.--i.e. more pressure is applied during a longer period of thecombustion stroke. Further, the area under this curve represents thegross indicated work per cylinder--which is also higher in the engineaccording to the invention. The more even application of pressure thepiston surface also introduces less undesirable vibration into thecombustion process.

The smooth burn according to the invention also leads to reduced NO_(x)emissions. As will be appreciated by one skilled in the art, the higherthe peak temperature, the greater the possibility of NO_(x) production.By maintaining the lesser peak temperature of combustion in the presentengine, the NO_(x) emissions are reduced as shown in FIG. 15. Theconfiguration of this engine maintains this lower peak temperature,while still exhibiting THC emission valves comparable to the stockengines. Typically, however, this reduced peak temperature would lead tohigher THC because lower temperature means a less efficient burn. Theunique characteristics of the present combustion apparently leads toboth lower peak temperature and complete burning of the charge. This maybe due to the burn occurring over a longer period of the piston's strokethan a conventional engine, such that the potential exists for morecrevice volume to be exposed to combustion, and to thus burn as well.This effect is further-enhanced by the scrubbing action, describedpreviously.

VALVE LUBRICATION AND COOLING

The engine 10, according to the invention is also designed for improvedvalve lubrication, cooling and ease of servicing and adjustment. Asdiscussed in regard to FIG. 1, the engine 10 includes L-shaped rockerarms 65 and 75, which are housed within generally P-shaped rocker armbrackets 66 and 76. Each rocker arm bracket is held in place by twobolts one disposed horizontally 77, and one disposed vertically 78.Assuming head cover 90 is removed, rocker arm bracket 76 and itsassociated rocker arm 75 can be easily removed by removing bolt 77 and78 and simply lifting the bracket and arm out of the cylinder head. Thismakes the bracket and rocker arm easy to service.

The operation of a representative rocker arm 75 can be seen most clearlyin reference to FIG. 2. The L-shaped arm 75 includes a cam pad 170disposed at the end of arm 171. Unlike a conventional single overheadcam configuration, it should be noted that the cam pad 170 is disposedbelow the cam shaft 80. This leads to advantageous lubrication andfunctional features as will be described in greater detail below. Thedepending arm 172 of the bracket 75 engages the valve train of valve 100at an actuating end 174. As the rocker arm in FIG. 2 is pivoted in thecounter-clockwise sense by virtue of the cam shaft 80 rotating in aclockwise sense, the valve 100 is disengaged from the exhaust port 105by the actuating end 174 pushing the valve train to the right in thesense of FIG. 2. A valve spring 195 biases valve 100 toward the closedposition.

An isolated perspective view of the rocker arm 75 and valve 100 areshown in FIG. 19, and an exploded view is shown in FIG. 20. Theactuating end 174 of the rocker arm 75 engages a valve shoe 200 which isentrained on stem 107. The valve shoe 200 is disposed on the valve stem107 between a valve guide 205 and a rear bearing sleeve 210. Head 105 isdisposed at the end of stem 107. As can be seen in FIGS. 3 and 4, thevalve guide is stationary in the cylinder head, while the stem 107reciprocates with respect to the guide 205. As can be seen most clearlyin FIG. 19, the valve guide 205 includes a curved bearing surface forreceiving the curved actuating end 174 of the rocker arm 75. Valve guide205 includes the curved bearing surface for two reasons. First of all,it allows the guide to adequately support the rocker arm 75. Secondly,the extended bottom section of the guide serves as a reservoir forlubricating oil, insuring adequate lubrication between arm 75 and guide205. The threaded end at stem 107 is fed through the central hole invalve shoe 200 and rear sleeve 210. Threaded bolt 220 fits within thecentral hole of rear sleeve 210, and is interior threaded to receive thethreads of stem 107. A compression-type oil ring 230 is also disposed onthe shaft 107. As will be appreciated by one skilled in the art, the oilring is disposed on the stem to prevent leakage of oil out of the valveand into the combustion chamber. The various components of valve 100 aredesigned and made to be light weight. A stock spring 195 may be used toachieve necessary valve actuation.

The valve according to this embodiment also includes numerous featuresleading to improved valve cooling. The stem 107 has a thicker region107a, which tapers to a thinner region 107b. The presence of the thickerregion 107a gives the valve an increased radiating surface leading tobetter valve cooling. According to a further aspect of the invention,the valve 100 also includes a hollow interior region. A section view ofvalve 100 is shown is FIG. 21, and shows the hollow region 108. Thepresence of this region further increases the radiating area availablefor heat dissipation. Thus, unlike thinner, solid conventional valves,the valves according to the invention have both a larger outsidediameter and radiating surface and a large inner radiating surfaceprovided by hollow region 108. Furthermore, despite the fact thatconventional valves have a theoretical cooling by virtue of heat flowfrom the head to the stem, this cooling is largely non-existent. Becauseof the significant length of conventional valve systems, that coolingmechanism is secondary to the cooling mechanism of heat flow from thevalve head to the valve seat. Of course, this primary cooling mechanismis unavailable when the conventional valve is open, i.e. not in contactwith the seat. Because of the shorter, thicker stems and the presence ofthe hollow region allowing both inner and outer radiating areas, thevalves of the present invention include improved heat transfermechanisms. These mechanisms are also always available to the valve, andare not dependent on the valve contacting a valve seat.

Further still, the valve 100 may also include oil ports 108a allowingcommunication of circulating oil into hollow region 108. The pressurizedoil will enter region 108 through the ports 108a and contact the innersurface of the valve in order to carry away heat. The valves also staycooler since they are shorter than stock valves, and thus have a shorterthermal distance from head to stem. Further, the valves are coolerbecause, at least in the case of the exhaust valve, the stem isretracted from the exhaust path during exhaust, keeping that valvecooler by preventing exposure of the stem to super hot exhaust gas. Thesame exhaust stem is then cooled by cold intake charge during the intakestroke. The valves according to the invention are thus light weight andexhibit improved temperature characteristics, leading to less thermaldistortion.

The configuration of the rocker arm brackets, rocker arms and tiltedvalves leads to improved lubrication characteristics for this engine. Ascan be seen in FIG. 1, and the top view of FIG. 18, the rocker armbrackets include elongated central openings 250. These elongated centralopenings 250 receive the horizontally extending arms of the respectiverocker arms. At the same time, the openings serve as oil reservoirs. Theupstanding sidewalls of the central openings 250 and the top surface ofthe rocker arm define a reservoir for collecting oil and maintaining therocker arm and its associated cam pad under more constant lubrication.On either side of the rocker arms within elongated central openings 250are leak crevices indicated generally by reference numeral 255 in thetop view of FIG. 18. These leak crevices allow lubricating oil to leakalong the depending portion of the rocker arms and into the valve trainassembly. Thus, lubrication of both the rocker arm and the valve trainare assisted by gravity. This is in distinction to the conventionalsingle overhead cam configuration where the cam pads are located abovethe cam shaft. In that case, oil must be thrown upward to lubricate thecam pad cam shaft surfaces. Of course, gravity works against such alubrication system. Similarly, this structure represents an improvementover the conventional dual overhead cam arrangement. In such anarrangement the buckets which house the spring end of the valve trainare located below their respective cam shafts. However, the dualoverhead cam design does not provide for pooling of the lubrication oilas in the present design. Accordingly, run off due to gravity is alsopresent in that design. Further, conventional valves rely on plannedleakage of oil to adequately lubricate the valve stem/bearing sleeveinterface. This is an imperfect, but workable system. It can lead,however to undesirable results. For example the leakage of oil throughan intake valve is enhanced, as compared to that through an exhaustvalve, by virtue of the fact that the intake valve must contain vacuum.In the present invention, however, valve lubrication is controlled asopposed to relying on designed-in leakage in the manner of conventionalengines. For instance, because the present valves are not sitting in themanifold, the stems behind the compression rings can be bathed in oil-asopposed to receiving minimal, leakage oil as in standard valves.Moreover, the circulation of oil through the present valves not onlyenhances lubrication, but also serves a cooling function, describedabove. The present valves are thus both cooler and better lubricatedthan conventional valves.

Gravity also assists the lubrication system in the present invention byvirtue of the fact that the valves may be tilted in a preferredembodiment. Accordingly, lubricating oil in the valve tends to run awayfrom the rings and the combustion chamber. Accordingly, when the engineis shut down lubricating oil that may typically leak into the combustionchamber will be drawn by gravity away from the combustion chamber andinto the spring end of the valve train. Of course, prevention of leakageof oil into the combustion chamber increases engine efficiency and alsoreduces hydrocarbon emissions generated by burning oil as opposed to afuel-air mixture. Thus, instead of gravity working against thelubrication system as in conventional single and dual overhead camconfigurations, the design according to the present invention usesgravity to enhance the lubrication system.

ENHANCEMENTS

While the engine just described has superior performance and emissionscharacteristics as compared to a stock engine, it is believed thatfurther improvements to the engine would lead to even greaterperformance and emissions characteristics. As will be appreciated by oneskilled in the art, the only meaningful way to analyze an theperformance of an engine is to conduct empirical studies on a prototype.While a prototype was built according to the previous embodiment, noprototype, to date, has been built incorporating the following potentialimprovements. Accordingly, the asserted advantages are at presentsomewhat theoretical, although soundly based on existing engine designprinciples and experience gained by testing and analysis of the previousembodiment. Thus, these improvements are also included within the scopeof the invention.

A first improved feature could be an increased compression ratio. Highcompression is important in an engine according to the invention sincethe engine features a high surface to volume ratio in the combustionchamber. It is believed that a higher compression ratio would result ineven lower unburned hydrocarbon emissions. Modification of both atapered piston crown and the thin upstanding combustion chamber sectionswill lead to this higher compression ratio.

Another possible improved feature of the engine would be reduction ofcrevice volumes. As is known to those skilled in the art, crevicevolumes are small volumes that occur at the proximity or joining of anytwo entities within the combustion chamber. In the embodiment previouslydescribed, an example of such a crevice volume is the joint between thevalves and the valves seat, where a significant crevice is formedbecause of the seating angles. Another crevice volume in thepreviously-described embodiment is the thin volume between the pistoncrown and the complemental interior surface of the cylinder head.Crevice volumes create a problem in that they form a very acceptableplace for unburned charge to hide, thus preventing the charge from beingthoroughly combusted. In the embodiment previously-described, thewedge-shaped piston crown resulted in two very large and isolatedcrevice volumes between the curved portions joining each crown face andthe complementally-shaped surface in the head. These crevice volumes canbe seen most clearly in FIG. 2. This problem could be potentially solvedby use of a cone-shaped piston, as shown in FIG. 22. This design isconsistent with the previous description of the piston crown tapering toa zenith along the central axis of the piston.

Such a design not only would reduce crevice volumes, but would also leadto increased combustion efficiencies. In the previously-describedembodiment, it is believed that the wedge-shape of the piston crown mayhave adversely affected the horizontal component of the complex swirlpattern of the combusting charge. This is due to the fact that theaxially extending joint line between the two wedge faces served as abarrier to the swirl which had to be surmounted during each period ofcirculation. Modification of the piston crown to be cone-shaped wouldeliminate this problem, while also helping to eliminate the crevicevolume problem.

Modification of the piston head to a cone shape could further becombined with a modification to the combustion chamber, as shown in FIG.23. In this design, the two halves, 501 and 502, of the combustionchamber are still offset about a longitudinal axis as in the previousembodiment, but they are joined at the bottom instead of the top. As aresult, the two separate flame fronts generated in each half of thecombustion chamber will not interact until just before the flame frontsenter the compression end 505 of the cylinder. Of course, such a designrequires each chamber half to have its own spark plug 511, 512. It isbelieved that this design will further enhance the swirling andscrubbing action of the combusting charge. Each chamber will have avalve neck 503 associated therewith (FIG. 24) to serve as a source ofswirl for the flame front, and the two halves of the exiting charge willbe more accurately directed so as to be thrown out against the cylinderwalls with even greater intensity leading overall to a more thoroughburn, while maintaining the other advantageous combustioncharacteristics of the preferred embodiment.

A further potential improved feature in the engine would be a reducedsurface to volume ratio. This could be achieved by having a more compactcombustion chamber, as well as a reduced surface area at the pistoncrown. Since less surface area will be available for clinging, unburnedhydrocarbons, the lower surface to volume ratio should produce lessunburned hydrocarbons.

A possible improvement could also be realized by increasing the valvesize, which brings the possibility of improved breathing. An example ofsuch a valve is seen in FIG. 25. Valve 550 has an even larger diameterthat in the previous embodiment. Further, the hollow central cavity 555has been extended the entire length of the valve. This not only allowsfor a significant increase in the internal radiating surface area, butsignificantly decreases valve mass and also allows the valve actuationspring 560 to be housed within the valve, as seen in FIG. 24. Thisgreatly simplifies the structure and actuation of the valve. Instead ofthe relatively heavy rocker arms from the previous embodiment, thisvalve can be actuated by a light-weight push rod 570 engaging a valveboot 575. FIG. 24 shows a simplified valve boot 575. An alternativeembodiment of boot 575' is shown in FIGS. 26 and 27. Boot 575' engages aring 580 disposed on the valve 550. The boot, including an angledcamming surface 585, includes a cutout 577 to reduce its mass whileproviding enhanced valve actuation. The boot, having a larger diameterthan the valve, would ride on linear tracks on the inside wall of thevalve sleeve, thus ensuring that the boot exerts only axial force of thevalve.

A reduced weight in the valve actuation system should result in lowerreciprocating mass, better lubrication, adjustment capabilities,cooling, and RPM capability. A simple mechanism may also be included sothat the valves rotate during actuation. Rotation of the valves allowsfor more uniform heating of the valves, thus preventing the formation ofhot spots which can cause valve distortion and knock during combustion.Cooling of the valve may also be enhanced by directing pressurized oilin the large hollow central cavity 555, the oil contacting the interiorsurface and carrying away heat.

An improvement of the design of the intake manifold could also lead toimproved performance. In the previously-described embodiment, the intakemanifold was fabricated with the use of simple carburation as the fueldelivery system. As is common with such systems, the cylinder furthestfrom the carburetor ran lean, while the cylinder closest to thecarburetor ran with the richest mixture. Improvement could be achievedby use of a more accurate, functional and runner-equalized intakemanifold, as well as by use of electronic fuel injection as opposed tocarburation.

Another possible improved feature would be a reduced piston mass. In thepreviously-described embodiment, a prototype was made using a modifiedand existing casting to obtain the necessary piston crown shape. As aresult, the piston had a weight that represented a 50 percent increaseover a stock piston. By using a cone-shaped piston of reduced mass,significant improvement should be realized.

Of course, as with any engine, improvements could also be realized byproperly adjusting an optimizing the timing of the engine. Further, anymodifications which improve the serviceability or access to parts of theengine is preferred. Prevention of oil leakage and improved coolingcapabilities are also desirable modifications to make to any engine.

While the above described modifications may potentially improve theperformance of an engine according to the invention, thepreviously-described embodiment realizes a significant advancement overstock engines, as shown graphically in FIG. 15. That engine was able toachieve better mileage, and reduced emissions because of the uniquestructure of the engine. This structure lead to the improved functionalcharacteristics described. In particular, the structure of the engineleads to an improved squish and swirl of the charge during thecompression stroke. The shape of the combustion chamber, the extensionof the valve stems across that chamber the shape of the piston head andthe complemental shape of the cylinder head combine to lead to acombustion-induced vertical and horizontal swirling of the charge duringthe power stroke. This leads to a smoother, more even burn as well as ascrubbing action for removing unburned hydrocarbons from the combustionchamber walls. The tapered piston crown contributes to the improvedperformance as the swirling charge exiting from the thin, upstandingcombustion chamber sweeps outwardly by contact with that crown-shapedhead to further induce swirl and lead to a more complete burn of thecharge as well as scrubbing of the cylinder walls. The design disclosedherein also offer lighter valves with enhanced cooling, lubricating andactuating capabilities.

There has thus been disclosed and improved internal combustion engine.Potential improvements have also been disclosed, and are intended to bewithin the scope of the present invention. Indeed, the inventionembraces all modifications and equivalents to the disclosed embodimentas fall within the scope of the following claims.

What is claimed is:
 1. An internal combustion engine having a blockincluding a piston cylinder having a longitudinal axis, and with apiston reciprocable therein, the combination comprising a cylinder headsecured to the block and serving as a closure for the compression end ofthe cylinder, a piston crown, the crown being tapered to a zenithcoincident with the longitudinal axis of the piston, an interior surfacein the cylinder head that is adjacent the compression end of thecylinder, the interior surface having a shape that is complemental tothe piston crown for receiving the piston crown at the top of itsstroke, a thin upstanding combustion chamber disposed vertically abovethe compression end of the cylinder and including a throat incommunication with the interior surface, the combustion chamberincluding two adjacent sections, each section having a longitudinalaxis, such that the longitudinal axes are at an angle to each othergreater than zero, and each section being spaced apart with respect toeach other relative to the longitudinal axis of the piston for dividinga combusting charge into separate entities, the adjacent sections beingdirected toward opposing regions on the piston crown to induce ahorizontal swirling of the exiting charge, a poppet valve associatedwith each adjacent section, each poppet valve mounted for reciprocationin a direction transverse of the longitudinal axis, a port in the faceof each adjacent section, each poppet valve including a head engagingthe port and a valve neck extending across the adjacent section withwhich the valve is associated, the valve neck being a source of inducedswirl to a compressing charge in each of the sections, and to acombusting charge in each of the sections, whereby vertical swirl isinduced in the respective charges when they circulate around the valvenecks.
 2. The internal combustion engine according to claim 1, whereinthe piston crown is wedge-shaped.
 3. The internal combustion engineaccording to claim 1, wherein the piston crown is conical.
 4. Theinternal combustion engine according to claim 1, wherein each poppetvalve is disposed in perpendicular relation to the port against which itengages, such that the valves are disposed at a downward angle, wherebylubricating oil associated with a given valve is moved by gravity awayfrom the combustion chamber.
 5. The internal combustion engine accordingto claim 1, wherein each poppet valve includes a stem with an internalhollow region to provide increased heat radiating surface area.
 6. Theinternal combustion engine of claim 5, wherein each poppet valveincreases at least one oil port in communication with the hollow region,to provide circulation of oil through the hollow region.
 7. A method ofcombusting hydrocarbon fuels in an internal combustion engine comprisinga piston crown tapered to a zenith coincident with a longitudinal axisof the piston and a combustion chamber divided into two sections eachbeing angled with respect to the longitudinal axis of the piston anddirected towards one of opposing regions on the piston crown, the methodcomprising the steps of:mixing a fuel and air charge by inducing aswirling of the charge as it enters the combustion chamber; igniting thecharge in the combustion chamber to generate a flame front; causing theflame front to exit the combustion chamber whereupon the flame front isdivided as a result of its interaction with the configuration of thecombustion chamber; and swirling the flame front by causing the flamefront to interact with the piston crown; whereby the swirling of theflame front serves to scrub the side walls of the cylinder and to assistin maintaining a slow, even burn of the charge.